Hydraulic valve control apparatus for internal combustion engines

Abstract

A hydraulic valve control apparatus in an embodiment for multi-cylinder internal combustion engine having a reservoir chamber, assigned to a pressure chamber of a valve tappet and having a reservoir piston that serves as a valve, with which the reservoir chamber can be separated from the pressure chamber. The reservoir piston is shifted out of its position of repose to a reservoir function by a hydraulic thrust that is conducted in the reservoir chamber under the control of a magnet valve, via a control line in which a check valve is disposed. Displacement of the reservoir piston occurs only whenever a valve actuation takes place via the drive cam and as a result the working pressure adequate for the displacement of the reservoir piston prevails in the pressure chamber.

We claim: 
     
       1. A hydraulic valve control apparatus for internal combustion engines, comprising: an engine valve axially driven by a drive cam of an engine camshaft via a valve tappet,   a pressure chamber (19) of variable volume determining an effective length of the valve tappet,   a fluid reservoir (22) connectable with the pressure chamber via a pressure conduit (21) and said fluid reservoir having a spring-loaded reservoir piston (23) that on its face end defines a reservoir chamber (26),   a magnet valve (34) that is triggered via an electronic control unit that processes engine parameters for controlling fluid flow to said fluid reservoir,   said reservoir piston (23), as a movable element, controls a connection between said pressure conduit (21) and the reservoir chamber (26),   said reservoir piston is engaged by a reservoir spring (24) and biased to a position closing said pressure conduit connection to said fluid reservoir, the reservoir piston (23) having a pressure shoulder (43) acting counter to the force of the reservoir spring (24) and always acted upon by the pressure in the pressure conduit (21) is present on a control line (35) including a one-way check valve (36) that opens in a direction toward the reservoir chamber (26) for controlling said fluid at a predetermined control pressure that discharges into the reservoir chamber (26), the control line being controlled by said magnet valve (34),   and a spring force engaging the reservoir piston (23) by means of the reservoir spring (24) is greater than a control force engaging the reservoir piston (23) as a result of the control pressure but less than an actuation force that is produced whenever an end face of the reservoir piston (23) is exposed to a working pressure of the pressure chamber when the valve tappet is actuated by the drive cam (4) in an opening direction.   
     
     
       2. A valve control apparatus as defined by claim 1, in which the force of the reservoir spring (24) is greater than the control force plus a pilot pressure force of said pressure in the pressure chamber before said valve tappet is actuated by the drive cam effected by the pressure shoulder (43). 
     
     
       3. A valve control apparatus as defined by claim 1, in which a relief line (47) that contains a backup throttle branches off from the reservoir chamber. 
     
     
       4. A valve control apparatus as defined by claim 2, in which a relief line (47) that contains a backup throttle branches off from the reservoir chamber. 
     
     
       5. A valve control apparatus as defined by claim 3, in which the relief line (47) is controlled by a pressure holding valve (46). 
     
     
       6. A valve control apparatus as defined by claim 4, in which the relief line (47) is controlled by a pressure holding valve (46). 
     
     
       7. A valve control apparatus as defined by claim 3, in which the relief line (47) is disposed in a bottom of the reservoir piston (23) and connects the reservoir chamber (24) to the reservoir spring chamber (48). 
     
     
       8. A valve control apparatus as defined by claim 5, in which the relief line (47) is disposed in a bottom of the reservoir piston (23) and connects the reservoir chamber (24) to the reservoir spring chamber (48). 
     
     
       9. A valve control apparatus as defined by claim 1, in which a pilot pressure reservoir (37) is connected, upstream of the magnet valve (34), to a feed line (31) for the control fluid. 
     
     
       10. A valve control apparatus as defined by claim 2, in which a pilot pressure reservoir (37) is connected, upstream of the magnet valve (34), to a feed line (31) for the control fluid. 
     
     
       11. A valve control apparatus as defined by claim 3, in which a pilot pressure reservoir (37) is connected, upstream of the magnet valve (34), to a feed line (31) for the control fluid. 
     
     
       12. A valve control apparatus as defined by claim 5, in which a pilot pressure reservoir (37) is connected, upstream of the magnet valve (34), to a feed line (31) for the control fluid. 
     
     
       13. A valve control apparatus as defined by claim 7, in which a pilot pressure reservoir (37) is connected, upstream of the magnet valve (34), to a feed line (31) for the control fluid. 
     
     
       14. A valve control apparatus as defined by claim 1, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       15. A valve control apparatus as defined by claim 2, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       16. A valve control apparatus as defined by claim 3, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       17. A valve control apparatus as defined by claim 5, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       18. A valve control apparatus as defined by claim 7, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       19. A valve control apparatus as defined by claim 9, in which the magnet valve (34) is embodied as a 2/2-way magnet valve. 
     
     
       20. A valve control apparatus as defined by claim 19, in which the force of the reservoir spring (24) is less than an opening force embodied by a sum of the control pressure and a fluid pressure created by the drive cam on the pressure shoulder (43) of the reservoir piston, and that a filling line (39) is controlled by the reservoir piston (23), wherein after the connection between the pressure conduit (21) and reservoir chamber (26) is established, the filling line (39) is blocked. 
     
     
       21. A valve control apparatus as defined by claim 20, in which on a jacket face of the reservoir piston (23) there is a longitudinal groove (54), which is in constant communication with an annular groove (53) present in a bore receiving the reservoir piston (23) and which in a position of repose communicates with the pressure conduit (21), but is separated from the pressure conduit (21) after the reservoir piston (23) is displaced counter to the force of the reservoir spring (24). 
     
     
       22. A valve control apparatus as defined by claim 1, in which the pressure conduit (21) communicates via a filling line (39) with a supply line (31) that is under a second control pressure, and that a check valve (41) opening in the direction of the pressure conduit (21) is disposed in the filling line (39). 
     
     
       23. A valve control apparatus, as defined by claim 1, for a multi-cylinder internal combustion engine, in which via an electronic control unit, various valve control units are each controllable only up to a drive of 180° of crankshaft rotation angle, so that a plurality of valve control units are controlled by only one magnet valve (34), and overlapping of control times. 
     
     
       24. A valve control apparatus as defined by claim 23, in which groups of valve control units, after a first division of the control line downstream of the magnet valve (34), are controllable by at least one preselection valve (51, 52). 
     
     
       25. A valve control apparatus as defined by claim 24, in which the preselection valve is embodied as a 2/2-way valve (51). 
     
     
       26. A valve control apparatus as defined by claim 24, in which a 3/2-way valve simultaneously effecting a division serves as the preselection valve.